Gonorrhoea bacteria. Coloured transmission electron micrograph (TEM) of a Neisseria gonorrhoeae bacteria diplococci (pair of cells, light orange) infecting a human epithelial cell (dark orange). This Gram-negative bacteria causes the sexually transmitted infection gonorrhoea. Symptoms include a vaginal or urethral discharge and a burning sensation on urination. However, the majority of infected women develop no symptoms. Treatment is with antibiotics.